Transcript

1.
The Dynamic CrustThe Dynamic Crust

2.
The Dynamic CrustThe Dynamic Crust
I.I. Evidence of Crustal Changes –Evidence of Crustal Changes – or HOW do we knowor HOW do we know
that movement of rocks takes place on Earth?that movement of rocks takes place on Earth?
A. Deformed Rock Structure - Sedimentary strataA. Deformed Rock Structure - Sedimentary strata
normally form in anormally form in a horizontalhorizontal position. Any change. Any change
from the horizontal position is evidence offrom the horizontal position is evidence of minorminor
crustal changecrustal change

10.
 The crust contains bothThe crust contains both
oceanic crustoceanic crust which iswhich is
covered by our oceanscovered by our oceans
andand continental crustcontinental crust,,
that is the land on whichthat is the land on which
we live.we live.

14.
3. Theory of Continental Drift3. Theory of Continental Drift
a.a. Alfred WegnerAlfred Wegner ––
proposed the theory ofproposed the theory of
Continental Drift in theContinental Drift in the
early 1900’s.early 1900’s.
b.b. He proposed thatHe proposed that
approximately 200 mya,approximately 200 mya,
all the continents existedall the continents existed
as one large land massas one large land mass
which he calledwhich he called
Pangaea.Pangaea.

15.
Dynamic CrustDynamic Crust
 SCRAT’s take on Plate TectonicsSCRAT’s take on Plate Tectonics
 For your viewing pleasure onlyFor your viewing pleasure only
 Don’t believe everything you see in theDon’t believe everything you see in the
movies....hahamovies....haha

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C. Evidence for Continental DriftC. Evidence for Continental Drift
1.1. Coastline of theCoastline of the
continents – forcontinents – for
example, the eastexample, the east
coast ofcoast of SouthSouth
AmericaAmerica fits wellfits well
with the west coastwith the west coast
ofof AfricaAfrica – like the– like the
pieces of a giantpieces of a giant jig-jig-
saw puzzle.saw puzzle.

18.
GlossopterisGlossopteris – it was an ancient seed-fern– it was an ancient seed-fern
(with very large heavy seeds). It’s fossils are(with very large heavy seeds). It’s fossils are
found infound in Africa,Africa, India , Australia, Antarctica and
South AmericaSouth America

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3. Rock Clues3. Rock Clues
a.a. TheThe AppalachianAppalachian
Mountains of the easternMountains of the eastern
US are geologicallyUS are geologically
similar to the mountainssimilar to the mountains
in Greenland andin Greenland and
western Europe, whichwestern Europe, which
include the Caledonianinclude the Caledonian
Mountains of Scotland.Mountains of Scotland.
b.b. Structure, age, andStructure, age, and
mineral content of rocksmineral content of rocks
are similar on the coastsare similar on the coasts
of easternof eastern SouthSouth
America and westernAmerica and western
Africa.Africa.

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4.4. Climate CluesClimate Clues
a.a. Coal, which formsCoal, which forms
from plants thatfrom plants that
grow in warmgrow in warm
swampyswampy
environments, isenvironments, is
found today in thefound today in the
colder climates ofcolder climates of
North America andNorth America and
Antarctica.Antarctica.

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b. Coral limestone, containing the remains of coral,, containing the remains of coral,
which once lived inwhich once lived in warm seaswarm seas, is found today in, is found today in
northern latitudes such asnorthern latitudes such as North CarolinaNorth Carolina..

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c.c. Ancient rocks of theAncient rocks of the
same agesame age near thenear the
equator in Southequator in South
America, SouthAmerica, South
Africa and otherAfrica and other
southernsouthern
landmasses showlandmasses show
evidence ofevidence of
glaciationglaciation..

23.
Continental Drift LabContinental Drift Lab
 Questions?Questions?
4. Where in the4. Where in the
United States isUnited States is
therethere
measurablemeasurable
evidence thatevidence that
the continentsthe continents
are movingare moving
relative to onerelative to one
another?another?

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C. The Theory of Plate TectonicsC. The Theory of Plate Tectonics
1.1. The Theory of Plate Tectonics states that Earth’sThe Theory of Plate Tectonics states that Earth’s
lithospherelithosphere (crust + upper mantle) is divided into(crust + upper mantle) is divided into
sections calledsections called lithospheric plateslithospheric plates..

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2.2. Plate MotionPlate Motion – The theory of Plate Tectonics states– The theory of Plate Tectonics states
that these lithospheric plates are in motion and “float”that these lithospheric plates are in motion and “float”
or ride on theor ride on the asthenosphereasthenosphere..

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3.3. Direction of Plate Movement – the movement and interaction of tectonicDirection of Plate Movement – the movement and interaction of tectonic
plates creates 3 types of plate boundaries: the arrows on the tectonicplates creates 3 types of plate boundaries: the arrows on the tectonic
map in your notes show the relative motion.map in your notes show the relative motion.

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D.D. Convection CurrentsConvection Currents == the driving force beneaththe driving force beneath
plate tectonicsplate tectonics
 Hot,Hot, LESSLESS densedense
material from deepmaterial from deep
within Earth’s mantlewithin Earth’s mantle
rises. When this materialrises. When this material
cools near the surface, itcools near the surface, it
becomesbecomes MOREMORE densedense
and sinks. The resultingand sinks. The resulting
convective flow of thisconvective flow of this
material in the mantlematerial in the mantle
CARRIES/MOVESCARRIES/MOVES
lithospheric plates acrosslithospheric plates across
the surface of Earth.the surface of Earth.
Label the diagram in your
notes according to this
diagram!

56.
1. Analysis of seismic
waves has led
scientists to infer the
layerslayers of earth.
b. Earthquake Waves and Earth’s Interiorb. Earthquake Waves and Earth’s Interior

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b. Types of seismic wavesb. Types of seismic waves
 P WavesP Waves = P or Primary Waves- Also known as= P or Primary Waves- Also known as
CompressionCompression waves - travel 6 mpswaves - travel 6 mps
 Motion of matter due to P waves-alternate contractionMotion of matter due to P waves-alternate contraction
and expansion of rocks in a direction parallel to theand expansion of rocks in a direction parallel to the
direction of wave propagation.direction of wave propagation.

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b. Types of seismic wavesb. Types of seismic waves
 S or Secondary Waves- Also known asS or Secondary Waves- Also known as Shear Waves andShear Waves and traveltravel atat
4 mps4 mps
 Motion of matter due to S waves-displacement of adjacent rocks inMotion of matter due to S waves-displacement of adjacent rocks in
a directiona direction perpendicularperpendicular to the direction of wave propagation.to the direction of wave propagation.
 The velocity of P and S waves is controlled by how the materialThe velocity of P and S waves is controlled by how the material
through which wave is traveling responds to shear forces. It alsothrough which wave is traveling responds to shear forces. It also
depends on thedepends on the densitydensity of the material.of the material.

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D. Locating the Epicenter
1. Need at least three (3) stations
2. Determine when P wave arrives
3. Determine when S wave arrives
4. Difference between S and P wave arrival ( t) EX: 4 min 20 seconds
5. Locate on travel-time curve what the ( t) corresponds to in distance
6. Draw circles around each station with radii=distance just determined
7. Intersection of three circles is the epicenter
Using Seismic Waves to Study Earthquakes

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•Seismic Waves travel
through the entire Earth
•Travel at different rates
through different densitiesdensities!
•That’s why the lines
“bendbend”…….when they go
through the layers
Earth’s structure/interior is
divided into the crust, mantle,
outer core and inner core.
E. Earthquake Waves

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F. Measuring an
Earthquake
1. Richter Scale –
a scale used to
express the
strength or
energy an
earthquake

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2. Mercalli Scale – a
scale used to show the
damage caused by an
earthquake by
assigning a number
from I to XII

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Using the Drawing CompassUsing the Drawing Compass
SUMMARYSUMMARY
 Read the seismograph times of P/S waveRead the seismograph times of P/S wave
 Or calculate the difference between the P-S waveOr calculate the difference between the P-S wave
arrival stationsarrival stations
 Use the graph on to determine the distance to theUse the graph on to determine the distance to the
epicenter.epicenter.
 Use the map scale to measure the distance from eachUse the map scale to measure the distance from each
of the 3 locations and draw a circle around each city.of the 3 locations and draw a circle around each city.
 The point of intersection of the 3 circles is theThe point of intersection of the 3 circles is the
EPICENTER!EPICENTER!